Highly selective visual detection of Cu(II) utilizing intramolecular hydrogen bond-stabilized merocyanine in aqueous buffer solution.

A Cu(2+)-specific colorimetric sensor 1, which is stabilized by an intramolecular hydrogen bonding, was designed and developed. The color of 1 changes from purple to blue on addition of 1.0 muM Cu(2+) in aqueous buffer solution, which can be detected by the naked eye. The analytical detection limit for Cu(2+) by the naked eye is as low as 1.0 muM. The stoichiometry for 1 and Cu(2+) in complex is 2:1 in aqueous solution.